Epoxy resin composition, process for producing epoxy resin, novel epoxy resin, novel phenol resin

ABSTRACT

In the technical field where a difunctional epoxy resin having increased molecular weight is used to impart flexibility or improving dielectric properties, the present invention has remarkably improved moisture resistance and water resistance when used to produce a cured epoxy resin article. The epoxy resin composition comprises a difunctional epoxy resin (A) having a structure wherein an aromatic hydrocarbon group (a1) having a bonding site in an aromatic nucleus and a hydrocarbon group (a2) having an ether bond or the other hydrocarbon group (a3) are bonded via an acetal bond (a4), and also has a structure wherein a glycidyloxy group is bonded to the aromatic hydrocarbon group (a1); and a curing agent (B) as essential component.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an epoxy resin composition whichexhibits excellent moisture resistance in a cured article, a process forproducing an epoxy resin used in the composition, a novel epoxy resin,and a novel phenol resin which is an intermediate of the novel epoxyresin.

Priority is claimed on Japanese Patent Application No. 2002-300212,filed Oct. 15, 2002, the content of which is incorporated herein byreference.

2. Description of Related Art

Epoxy resins are widely used in the fields of electronics and coatingswith high levels of functionality because cured articles thereofobtained by curing with various curing agents are excellent indimensional stability, electrical insulating properties and chemicalresistance. In the field of these epoxy resins, attempts of reducing thedensity of crosslinks of a cured article are made by using ahigh-molecular weight difunctional epoxy resin for the purpose ofimparting flexibility to the cured article or improving dielectricproperties dielectric properties in the fields of electrical andelectronic components.

In applications such as underfill materials in the field ofsemiconductor encapsulant and flexible wiring boards in the field ofelectrical laminates, which have recently been much in demand, there isrequired an epoxy resin which can produce cured articles which areflexible and excellent in toughness. As an epoxy resin having theserequired characteristics, for example, there is known an epoxy resinhaving increased molecular weight obtained by reacting a liquidbisphenol A type epoxy resin with an aliphatic dicarboxylic acid such asdimer acid or sebacic acid as a molecular chain extender (see, forexample, Japanese Unexamined Patent Application, First Publication No.Hei 8-53533 (pages 2 to 4)). However, the epoxy resin obtained by thistechnique is likely to be hydrolyzed and is inferior in moisture orwater resistance due to an ester bond existing in the molecularstructure.

As a technique which improves dielectric properties by reducing thedensity of crosslinks by way of increasing a molecular weight of anepoxy resin in applications such as semiconductor encapsulant, forexample, there is known a technique of introducing alicyclic structurein the chemical structure of an epoxy resin. For example, an epoxy resinwhich is given by glycidyl etherification of a phenol resin, which is apolyadduct of phenol and dicyclopentadiene, is known as an epoxy resinhaving improved dielectric properties for semiconductor encapsulant(see, for example, Japanese Unexamined Patent Application, FirstPublication No. 2001-240654 (claim 1, paragraph number [0009])).

Such an epoxy resin is excellent in moisture resistance and dielectricproperties and is a useful resin because it can lower a dielectricdissipation, but it is not sufficient in the effect of lowering thedielectric constant and it is difficult to apply the epoxy resin to asemiconductor of a high frequency type in the gigahertz range, which hasrecently been much in demand. Therefore, even if the epoxy resin havingan alicyclic structure in its chemical structure which is caused by, forexample, polyadduct of phenol and dicyclopentadiene, in order to furtherimprove dielectric propertiesdielectric properties such as lowdielectric constant and low dielectric dissipation factor of the epoxyresin, the viscosity increases and drastic deterioration of moistureresistance and water resistance is caused by the reaction between anepoxy group and a phenolic hydroxyl group, thereby deteriorating soldercracking resistance.

BRIEF SUMMARY OF THE INVENTION

Therefore, an object to be achieved by the present invention is toremarkably improve moisture resistance of the epoxy resin in thetechnical field where a difunctional epoxy resin having increasedmolecular weight is used for the purpose of imparting flexibility orimproving dielectric propertiesdielectric properties.

To achieve the above object, the present inventors have intensivelyresearched and found that a molecular weight of a difunctional epoxyresin can be increased by using a difunctional phenol resin, which isobtained by the acetalization reaction of a divinyl ether of analiphatic or aromatic hydrocarbon compound or a divinyl ether of anoxyalkylene compound with a difunctional phenol, as a raw material forepoxy resin without deteriorating moisture resistance or waterresistance of the epoxy resin. Thus, the present invention has beencompleted.

That is, the present invention relates to an epoxy resin compositioncomprising: a difunctional epoxy resin (A) having a structure wherein anaromatic hydrocarbon group (a1) having a bonding site in an aromaticnucleus and a hydrocarbon group (a2) having an ether bond or the otherhydrocarbon group (a3) are bonded via an acetal bond (a4), and also hasa structure wherein a glycidyloxy group is bonded to the aromatichydrocarbon group (a1); and a curing agent (B).

Furthermore, the present invention relates to a process for producing anepoxy resin, which comprises the steps of: reacting a difunctionalphenol compound (a1′) with a divinyl ether (a2′) of a hydrocarboncompound having an ether bond or a divinyl ether (a3′) of the otherhydrocarbon compound, and reacting the resulting phenol compound withepihalohydrin.

Furthermore, the present invention relates to a novel epoxy resinrepresented by the following general formula 1:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or a bromine atom, X represents an ethyleneoxyethyl group, adi(ethyleneoxy)ethyl group, a tri(ethyleneoxy)ethyl group, apropyleneoxypropyl group, a di(propyleneoxy)propyl group, atri(propyleneoxy)propyl group, or an alkylene group having 2 to 15carbon atoms, n is a natural number, and the average thereof is from 1.2to 5.

Furthermore, the present invention relates to a novel epoxy resinrepresented by the following general formula 2:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or a bromine atom, X represents a C₆₋₁₇ aliphatic hydrocarbon grouphaving a cycloalkane skeleton, n is a natural number, and the averagethereof is from 1.2 to 5.

Furthermore, the present invention relates to a novel epoxy resinrepresented by the following general formula 3:

wherein R₃ to R₆ each represents a hydrogen atom, a methyl group, achlorine atom, or a bromine atom, X each independently represents aC₆₋₁₇ aliphatic hydrocarbon group having a cycloalkane skeleton, n is anatural number, and the average thereof is from 1.2 to 5.

Furthermore, the present invention relates to a novel phenol resinrepresented by the following general formula 4:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or a bromine atom, and X represents an ethyleneoxyethyl group, adi(ethyleneoxy)ethyl group, a tri(ethyleneoxy)ethyl group, apropyleneoxypropyl group, a di(propyleneoxy)propyl group, atri(propyleneoxy)propyl group, or an alkylene group having 2 to 15carbon atoms, n is a natural number, and the average thereof is from 1.2to 5.

Furthermore, the present invention relates to a novel phenol resinrepresented by the following general formula 5:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or a bromine atom, X represents a C₆₋₁₇ aliphatic hydrocarbon grouphaving a cycloalkane skeleton, n is a natural number, and the averagethereof is from 1.2 to 5.

Furthermore, the present invention relates to a novel phenol resinrepresented by the following general formula 6:

wherein R₃ to R₆ each represents a hydrogen atom, a methyl group, achlorine atom, or a halogen atom, X each independently represents aC₆₋₁₇ aliphatic hydrocarbon group having a cycloalkane skeleton, n is anatural number, and the average thereof is from 1.2 to 5.

According to the present invention, in a high-molecular weight epoxyresin, water resistance and moisture resistance of its cured article areremarkably improved.

The epoxy resin composition of the present invention can be used incoatings because it has flexibility and toughness when using a flexibledifunctional epoxy resin (A). In this case, a coating film havingexcellent adhesion and bending properties is obtained. The epoxy resincan be used in structural materials such as CFRP (carbon fibrereinforced plastics) because of toughness. Furthermore, the epoxy resincan be used in materials such as underfill materials, adhesives forflexible wiring boards, and resist ink materials.

When using a low dielectric difunctional epoxy resin (A), the epoxyresin can be used in materials having low dielectric constant and lowdielectric dissipation factor, capable of coping with high-frequencyequipment, semiconductor encapsulant, printed circuit board materialsand build-up layer insulating materials.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a graph showing a ¹³C NMR spectrum of modified polyhydricphenols (ph-1a) obtained in Example 1.

FIG. 2 is a graph showing a ¹³C NMR spectrum of an epoxy resin (ep-1a)obtained in Example 2.

FIG. 3 is a graph showing a ¹³C NMR spectrum of a difunctional phenolresin (ph-1b) obtained in Example 12.

FIG. 4 is a graph showing a ¹³C NMR spectrum of a difunctional epoxyresin (ep-1b) obtained in Example 13.

FIG. 5 is a graph showing a ¹³C NMR spectrum of a difunctional phenolresin (ph-2b) obtained in Example 14.

FIG. 6 is a graph showing a ¹³C NMR spectrum of a difunctional epoxyresin (ep-2b) obtained in Example 15.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in detail below.

The difunctional epoxy resin (A) used in the present invention has astructure wherein an aromatic hydrocarbon group (a1) having a bondingsite in an aromatic nucleus and a hydrocarbon group (a2) having an etherbond or the other hydrocarbon group (a3) are bonded via an acetal bond(a4), and also has a structure wherein a glycidyloxy group is bonded tothe aromatic hydrocarbon group (a1)

The aromatic hydrocarbon group (a1) having a bonding site in an aromaticnucleus is a hydrocarbon group having a bonding site with the otherstructural unit in the aromatic nucleus in an aromatic hydrocarboncompound. Specific examples of the aromatic hydrocarbon group (a1)include:

-   -   (i) a hydrocarbon group having a structure of having only a        benzene ring,    -   (ii) a hydrocarbon group having a structure wherein a benzene        ring is bonded via a single bond,    -   (iii) a hydrocarbon group having a structure wherein a benzene        ring is bonded via a benzene ring is bonded via an aliphatic        carbon atom,    -   (iv) a hydrocarbon group having a structure wherein a benzene        ring is bonded via an aliphatic cyclic hydrocarbon group,    -   (v) a hydrocarbon group having a structure wherein plural        benzene rings are condensed into a polycycle structure, and    -   (vi) a hydrocarbon group having a structure wherein a benzene        ring is bonded via an aralkyl group.

Examples of the aromatic hydrocarbon group (i) include a phenylene grouphaving a bonding site at the o-, m-, and p-position.

Examples of the aromatic hydrocarbon group (ii) include 4,4′-biphenylenegroup and 2,2′,6,6′-tetramethyl-4,4′-biphenyl group.

Examples of the aromatic hydrocarbon group (iii) includemethylenediphenylene group, 2,2-propane-diphenyl group, and thoserepresented by the following structural formulas:

Examples of the aromatic hydrocarbon group (iv) include thoserepresented by the following structural formulas:

(Here, Bond-positions in the structure iv-1, and iv-3 are locatedindependently on secondary carbon atoms which belong to ethylene orpropylene consisting the aliphatic rings in the structures.)

Examples of the aromatic hydrocarbon group (v) include naphthalenegroups such as 1,6-naphthalene group and 2,7-naphthalene group,1,4-naphthalene group, 1,5-naphthalene group, 2,3-naphthalene group, andthose represented by the following structure:

Examples of the aromatic hydrocarbon group (vi) include thoserepresented by the following structure:

Among these, an aromatic hydrocarbon group represented by the structure(iii) is preferable and a methylenediphenylene group and a2,2-propane-diphenyl group are particularly preferable because theresulting cured epoxy resin article is excellent in balance betweenflexibility and toughness.

According to applications of the difunctional epoxy resin (A), achemical structure of the hydrocarbon group (a2) having an ether bond orthe other hydrocarbon group (a3) can be appropriately selected.

Since a cured epoxy resin article, which is flexible and is excellent intoughness, is required in applications such as underfill materials inthe field of semiconductor encapsulantsemiconductorencapsulantsemiconductor encapsulant and flexible wiring boards in thefield of electrical laminates, it is preferable that analkyleneoxyalkylene group (a2-1) be selected as the hydrocarbon group(a2) having an ether bond and a straight-chain alkylene group (a3-1)having 2 to 15 carbon atoms be selected as the other hydrocarbon group(a3) (hereinafter a difunctional epoxy resin having thealkyleneoxyalkylene group (a2-1) or the straight-chain alkylene group(a3-1) having 2 to 15 carbon atoms is referred to as a “flexibledifunctional epoxy resin (A)”).

According to the present invention, it is possible to produce a curedepoxy resin article having high flexibility, which has never beenachieved by the prior art, by applying the alkyleneoxyalkylene group(a2-1) or the straight-chain alkylene group (a3-1) having 2 to 15 carbonatoms. For example, the above-mentioned epoxy resin having increasedmolecular weight, which is obtained by reacting a liquid bisphenol Atype epoxy resin using an aliphatic dicarboxylic acid such as dimer acidor sebacic acid as a molecular chain extender, yields a cured epoxyresin article having a flexible structure, but its effect isinsufficient because of cohesion of ester groups.

In contrast, in the present invention, the alkyleneoxyalkylene group(a2-1) or the straight-chain alkylene group (a3-1) having 2 to 15 carbonatoms serves as a so-called soft segment which imparts flexibility tothe difunctional epoxy resin (A), and a cured article obtained by curingthe difunctional epoxy resin (A) becomes very flexible. In this case,since the aromatic hydrocarbon group (a1) serves as a so-called hardsegment which imparts stiffness to the flexible difunctional epoxy resin(A), the flexible difunctional epoxy resin (A) can yield a cured epoxyresin article having both flexibility and toughness.

The alkyleneoxyalkylene group (a2-1) may include ethyleneoxyethyl groupand poly(ethyleneoxy)ethyl group formed by the polyaddition reaction ofethylene oxide, propyleneoxypropyl group and poly(propyleneoxy)propylgroup formed by the polyaddition reaction of propylene oxide, and acombination of ethyleneoxy group and propyleneoxy group obtained by thepolyaddition reaction of ethylene oxide and propylene oxide.

The greater the number of alkylene units of the alkyleneoxyalkylenegroup (a2-1), the more the flexibility of the epoxy resin is improved.However, the toughness tends to be deteriorated because the crosslinkdensity is lowered. Therefore, the number of alkylene groups in thealkyleneoxyalkylene group (a2) is from 2 to 4 in view of balance betweenperformances.

The straight-chain alkylene group (a3-1) having 2 to 15 carbon atoms issubstantially composed of a straight-chain carbon atom chain. Althoughthe group may have a partially branched structure which does notadversely affect the flexibility, a straight-chain alkylene group havingno branching is preferable in view of the flexibility.

Among the poly(alkyleneoxy)alkyl group and straight-chain alkylene grouphaving 2 to 15 carbon atoms, the former is preferable because theflexibility is improved and also adhesion and bondability to a basematerial of the cured epoxy resin article are improved.

To produce a cured article which has excellent dielectricpropertiesdielectric properties suited for applications such assemiconductor encapsulantsemiconductor encapsulantsemiconductorencapsulant and printed circuit boards, low dielectric constant and lowdielectric dissipation factor, an aliphatic cyclic hydrocarbon group(a3-2) is preferably selected as the other hydrocarbon group (a3)(hereinafter a difunctional epoxy resin having the aliphatic cyclichydrocarbon group (a3-2) is referred to as a “low dielectricdifunctional epoxy resin (A)”).

Specific examples of the aliphatic cyclic hydrocarbon group (a3-2)include those having the following structures:

(Here, Bond-positions in the structure a3-2-2, a3-2-3, and a3-2-5 arelocated independently on secondary carbon atoms which belong to ethyleneor propylene consisting the aliphatic rings in the structures.)

Among these groups, those having the structure a3-2-2, a3-2-3, or a3-2-5are preferable in view of the fact that the stiffness of the epoxy resinitself is enhanced and a difunctional epoxy resin (A) having excellentdielectric propertiesdielectric properties is obtained, and on the otherhand, those having the structure a3-2-1 or a3-2-4 are preferable in viewof excellent balance between dielectric propertiesdielectric properties,heat resistance, moisture resistance and fluidity.

In the present invention, when using, as the other hydrocarbon group(a3), not only those having the above structures, but also aromatichydrocarbon groups having the following structures:

a polyarylene type difunctional epoxy resin (A) can be produced.

An acetal bond (a4), which is capable of bonding the aromatichydrocarbon group (a1) having a bonding site with the other group in anaromatic nucleus to the hydrocarbon group (a2) having an ether bond orthe other hydrocarbon group (a3), is represented by the followinggeneral formula 7:

In the general formula, R₇ is selected from hydrogen atom, methyl group,ethyl group, propyl group, and t-butyl group. Among these, a bondwherein R₇ is a methyl group, that is, a methylacetal bond is mostpreferable because it is easy to produce the difunctional epoxy resinitself and the flexibility of the cured epoxy resin article isremarkably improved.

The difunctional epoxy resin (A) can remarkably improve moistureresistance and water resistance of the cured epoxy resin article byusing, as a basic skeleton, a molecular structure wherein the aromatichydrocarbon group (a1) having a bonding site in an aromatic nucleus andthe hydrocarbon group (a2) having an ether bond or the other hydrocarbongroup (a3) are bonded via the bond (a3).

Particularly in the case of the flexible difunctional epoxy resin (A),when the aromatic hydrocarbon group (a1) serving as the hard segment andalkyleneoxyalkylene group (a2-1) or straight-chain alkylene group (a3-1)having 2 to 15 carbon atoms, which serves as the soft segment, arebonded via an acetal bond (a4), it becomes possible to impartflexibility to an epoxy resin structure and exhibit excellent waterresistance. In the present invention, the toughness of the cured epoxyresin article is remarkably improved by directly bonding a glycidyloxygroup to the aromatic nucleus. In a general-purpose epoxy resin having astructure wherein a diol compound obtained by modifying a low-molecularweight liquid bisphenol A type epoxy resin with ethylene oxide orpropylene, oxide is subjected to glycidyl etherification, the epoxyresin skeleton itself becomes flexible, but is inferior in activity ofan epoxy group itself and crosslinking sufficient to exhibit thetoughness during curing cannot be obtained. While in the flexibledifunctional epoxy resin (A), since the activity of the epoxy group isenhanced by directly bonding a glycidyloxy group to the aromaticnucleus, proper crosslinking is formed during the curing reaction toexhibit excellent toughness regardless of flexible resin. Furthermore,the hard segment adjacent to the epoxy group serving as a crosslinkpoint increases a physical strength at the crosslink point increases andimproves the toughness.

Specific chemical structure of the flexible difunctional epoxy resin (A)include chemical structure having any combination of the aromatichydrocarbon group (a1) having a bonding site with the other group in anaromatic nucleus, the alkyleneoxyalkylene group (a2-1) or the alkylenegroup having 2 to 15 carbon atoms (a3-1), and an acetal bond (a4).Examples thereof include those having the following structural formulas.

In the respective structures described above, n is a natural number, andthe average thereof is from 1.2 to 5. Bond-positions in the structureEa-16, are located independently on secondary carbon atoms which belongto ethylene or propylene consisting the aliphatic rings in thestructure. Examples of the compound represented by the respectivestructural formulas include resin having a substituent such as methylgroup or halogen atom in an aromatic nucleus.

Among these flexible difunctional epoxy resins (A), a novel epoxy resinrepresented by the following general formula 1:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or a bromine atom, X represents an ethyleneoxyethyl group, adi(ethyleneoxy)ethyl group, a tri(ethyleneoxy)ethyl group,propyleneoxypropyl group, a di(propyleneoxy)propyl group, atri(propyleneoxy)propyl group, or an alkylene group having 2 to 15carbon atoms, n is a natural number, and the average thereof is from 1.5to 5, of the present invention is particularly preferable because of theresulting cured epoxy resin article is excellent in balance betweenflexibility and toughness and is also excellent in water resistance.

Specific examples of the novel epoxy resin include the aforementionedepoxy resins of Ea-1 to Ea-14.

The low dielectric difunctional epoxy resin (A) has, as a basicskeleton, a molecular structure wherein the aromatic hydrocarbon group(a1) having a bonding site in an aromatic nucleus and the aliphaticcyclic hydrocarbon group (a3-2) are bonded via the acetal bond (a4).With such a structure, excellent dielectric propertiesdielectricproperties are achieved in the cured epoxy resin article because of suchfeatures that (1) the distance between crosslinking points increases andthe density of crosslinks decreases when the resin is cured and (2) nohydroxyl group exists in the bonding portion of the aromatic hydrocarbongroup (a1) and the aliphatic cyclic hydrocarbon group (a2). Furthermore,there is achieved a feature such that (3) even if the distance betweencrosslinking points increases during curing, the stiffness of the epoxyresin itself is maintained and the cured article is excellent inrigidity and strength of the cured article.

Specific chemical structure of the flexible difunctional epoxy resin (A)include chemical structure having any combination of the aromatichydrocarbon group (a1) having a bonding site with the other group in anaromatic nucleus, an aliphatic cyclic hydrocarbon group (a3-2) and anacetal bond (a3). Examples thereof include those having the followingstructural formulas.

In the respective structures described above, n is a natural number, andthe average thereof is from 1.2 to 5. Bond-positions in the structureEa-5 to 12, Ea-14 and Ea-15, are located independently on secondarycarbon atoms which belong to ethylene or propylene consisting thealiphatic rings in the structures. Examples of the compound representedby the respective structural formulas include resin having a substituentsuch as methyl group or halogen atom in an aromatic nucleus.

Among these flexible difunctional epoxy resins (A), a novel epoxy resinrepresented by the following general formula 2:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or a bromine atom, X represents a C₆₋₁₇ aliphatic hydrocarbon grouphaving a cycloalkane skeleton, n is a natural number, and the averagethereof is from 1.2 to 5, of the present invention is particularlypreferable because proper flexibility is imparted to the cured epoxyresin article while maintaining excellent dielectricpropertiesdielectric properties and the resulting cured epoxy resinarticle is excellent in toughness.

Specific examples of the novel epoxy resin include the aforementionedepoxy resins of Eb-1 to Eb-8.

Because of excellent dielectric propertiesdielectric properties,excellent heat resistance and water resistance as well as improvedfluidity, a novel epoxy resin represented by the following generalformula 3:

wherein R₃ to R₆ each represents a hydrogen atom, a methyl group, achlorine atom, or a halogen atom, X each independently represents analiphatic cyclic hydrocarbon group having 6 to 15 carbon atoms, n is anatural number, and the average thereof is from 1.2 to 5, of the presentinvention is particularly preferable.

Specific examples of the novel epoxy resin include the aforementionedepoxy resins of Eb-9 to Eb-12.

The epoxy resin composition of the present invention contains thedifunctional epoxy resin (A) as an essential epoxy resin component.However, the difunctional epoxy resin (A) can be used in combinationwith a component not having increased molecular weight, that is, adifunctional epoxy resin (A′) having a structure wherein a glycidyloxygroup is bonded to an aromatic nucleus of the aromatic hydrocarbon group(a1) having a bonding site in the aromatic nucleus.

When using the flexible difunctional epoxy resin (A) in combination withthe difunctional epoxy resin (A′), the viscosity of the epoxy resincomposition decreases and the operability in the case of application isimproved and the cured article is excellent in toughness.

Specific examples of the difunctional epoxy resin (A′) include those ofthe aforementioned structural formulas of Ea-1 to Ea-17 wherein n=0.Therefore, in the case of a mixture of the epoxy resins of thestructural formulas Ea-1 to Ea-17, the average of n is preferably withina range from 1 to 3.

An existing ratio of the flexible difunctional epoxy resin (A) to thedifunctional epoxy resin (A′), (A)/(A′), is preferably from 90/10 to60/40 by weight because the cured article is excellent in balancebetween toughness and flexibility. The mixture of the difunctional epoxyresin (A) and the difunctional epoxy resin (A′) preferably has an epoxyequivalent of 250 to 1000 g/eq and a viscosity at 25° C. of 2000 to150000 mPa·s. The mixture has a feature such that it has low meltviscosity and is not solidified regardless of comparatively high epoxyequivalent, and an epoxy resin mixture having flexibility, good adhesionand excellent operability can be obtained.

When using a low dielectric difunctional epoxy resin (A), it is toachieve good balance between melt viscosity of the epoxy resincomposition and performances of the cured article by using it in amixture with the difunctional epoxy resin (A′) having a structurewherein a glycidyloxy group is bonded to the aromatic nucleus of thearomatic hydrocarbon group (a1). For example, in the case in which thedifunctional epoxy resin (A′) has a structure represented by thefollowing general formula 8:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or a halogen atom, X each independently represents an aliphatic cyclichydrocarbon group having 6 to 15 carbon atoms, the toughness of thecured article is improved.

In the case in which the difunctional epoxy resin (A′) has a structurerepresented by the following general formula 9:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or bromine atom, and X represents a C₆₋₁₇ aliphatic hydrocarbon grouphaving a cycloalkane skeleton, it is possible to achieve good balancebetween heat resistance, water resistance and dielectricpropertiesdielectric properties.

Specific examples of the difunctional epoxy resin (A′) corresponding tothe general formula 8 include those of the aforementioned structuralformulas of Eb-1 to Eb-8 wherein n=0. Specific examples of thedifunctional epoxy resin corresponding to the general formula 9 includethose of the aforementioned structural formulas of Eb-9 to Eb-12 whereinn=0. Similarly, those of the aforementioned structural formulas of E-13to E-15 wherein n=0 are also included in the difunctional epoxy resin(A′). In the case of a mixture of epoxy resins of the structuralformulas Eb-1 to Eb-15, the average of n is preferably within a rangefrom 0.5 to 4.5.

An existing ratio of the flexible difunctional epoxy resin (A) to thedifunctional epoxy resin (A′), (A)/(A′), is preferably from 90/10 to60/40 by weight in view of balance between performances of the curedarticle. The mixture of the difunctional epoxy resin (A) and thedifunctional epoxy resin (A′) preferably has an epoxy equivalent of 300to 1000 g/eq and a viscosity at 25° C. of 20 to 500 mPa·s. Thedifunctional epoxy resin (A) has a feature such that it has highmolecular weight and is excellent in dielectric propertiesdielectricproperties because the distance between crosslinking points increasesduring curing, and it is also excellent in fluidity. Therefore, bycontrolling to the above mixing ratio, the fluidity of the epoxy resincomposition can be enhanced while maintaining excellent dielectricpropertiesdielectric properties and a filling factor of the inorganicfiller can be enhanced in applications such as semiconductorencapsulant.

In the production of the epoxy resin composition, the difunctional epoxyresin (A) and the difunctional epoxy resin (A′) can be used as a mixturethereof.

The difunctional epoxy resin (A) described above in detail can beproduced by acetalization of a difunctional phenol compound (a1′), adialcohol of a hydrocarbon compound having an ether bond or a dialcoholof the other hydrocarbon compound, and a carbonyl compound, and glycidyletherification of the resulting difunctional phenol.

However, it is preferably produced by the process of the presentinvention in view of good industrial productivity.

Therefore, the difunctional epoxy resin (A) is preferably produced byreacting a difunctional phenol compound (a1′) with a divinyl ether (a2′)of a hydrocarbon compound having an ether bond or a divinyl ether (a3′)of the other hydrocarbon compound (hereinafter this step is referred toas a “step 1”), and reacting the resulting difunctional phenol resinwith epihalohydrin (hereinafter this step is referred to as a “step 2”).Since the reaction product produced by this process is commonly obtainedas a mixture of a difunctional epoxy resin (A) and a difunctional epoxyresin (A′), the mixture can be used as it is as an epoxy resin componentin the present invention.

In the above process, an acetal bond is formed by the reaction between aphenolic hydroxyl group in the phenol compound (a1′) and a vinyl ethergroup in the above (a2′) or (a3′), as shown in the following reactionscheme.

Specific examples of the difunctional phenol compound (a1′) includedihydroxybenzenes such as hydroquinone, resorcin, and catechol;dihydroxynaphthalenes such as 1,6-dihydroxynaphthalene,2,7-dihydroxynaphthalene, 1,4-dihydroxynaphthalene,1,5-dihydroxynaphthalene, 2,3-dihydroxynaphthalene; and2,6-dihydroxynaphthalene; bisphenols such asbis(4-hydroxyphenyl)methane, 2,2-bis(4-hydroxyphenyl)propane,2,2-bis(3-methyl-4-hydroxyphenyl)propane,1,1-bis(4-hydroxyphenyl)cyclohexane,1,1-bis(4-hydroxyphenyl)-1-phenylethane, andbis(4-hydroxyphenyl)sulfone; alicyclic structure-containing phenols suchas polyadduct of phenol and dicyclopentadiene, and polyadduct of phenoland terpene compound; bisnaphthols such asbis(2-hydroxy-1-naphthyl)methane and bis(2-hydroxy-1-naphthyl)propane;and so-called xylok-type phenol resin, which is a condensation reactionproduct of phenol and phenylene dimethyl chloride or biphenylenedimethyl chloride. The difunctional phenol compound further includesdifunctional phenol compounds having a structure wherein a substituentsuch as methyl group, t-butyl group or halogen atom is substituted onthe aromatic nucleus of the above respective compounds. It should benoted that although the above alicyclic structure-containing phenols orxylok-type phenol resins may include not only difunctional componentsbut also trifunctional components at the same time, they can be used instep 1 as they are according to the present invention.

Among these, bisphenols are preferable because the resulting cured epoxyresin article is excellent in balance between flexibility and toughness,and bis(4-hydroxyphenyl)methane and 2,2-bis(4-hydroxyphenyl)propane areparticularly preferable because of their remarkable capability ofimparting toughness. Furthermore, in the case of focusing on themoisture resistance of the cured epoxy resin article, alicyclicstructure-containing phenols are preferable.

The divinyl ether (a2′) of the hydrocarbon compound having an ether bondis used to produce a flexible difunctional epoxy resin and isrepresented, for example, by the following general formula.

In the general formula 10, R₈ is a hydrogen atom or a methyl group, andm is 0 or a natural number of 1 to 4. When R₈ is a hydrogen atom, it hasa polyethylene glycol skeleton. When it is a methyl group, it has apolypropylene glycol skeleton.

In the present invention, R⁸ in the general formula 10 may have astructure wherein a hydrogen atom and a methyl group exist at random,that is, a structure of being copolycondensed with ethylene oxide orpropylene oxide.

In the case of producing a flexible difunctional epoxy resin, thedivinyl ether (a3′) of the other hydrocarbon compound is preferably adivinyl ether of an alkylene having 2 to 15 carbon atoms and examplesthereof include divinyl ethers of straight-chain alkylene groups, suchas polytetramethylene glycol divinyl ether, 1,3-butylene glycol divinylether, 1,4-butanedidiol divinyl ether, 1,6-hexanediol divinyl ether,1,9-nonanediol divinyl ether, and 1,10-decanediol divinyl ether; anddivinyl ethers of branched alkylene groups, such as neopentyl glycoldivinyl ether. Among these, divinyl ethers of straight-chain alkylenegroups are particularly preferable in view of the flexibility of thecured epoxy resin article.

Among these, a divinyl ether represented by the general formula 10 isparticularly preferable because the melt viscosity of the flexibledifunctional epoxy resin (A) decreases and the resulting cured epoxyresin article is excellent in toughness and flexibility, and thusbending properties, adhesion and bondability are improved. When usingthe divinyl ether, since an epoxy resin having high hydrophilicity isobtained because of its polyether structure, an aqueous or emulsion typeepoxy resin composition can be easily prepared.

In the case of producing the low dielectric difunctional epoxy resin(A), examples of the divinyl ether (a3′) of the other hydrocarboncompound include divinyl ethers having a cycloalkane structure, such as1,4-cyclohexane diol divinyl ether, 1,4-cyclohexane dimethanol divinylether, tricyclodecane diol divinyl ether, tricyclodecane dimethanoldivinyl ether, pentacyclopentadecane dimethanol divinyl ether, andpentacyclopentadecane diol divinyl ether.

In the case of producing a polyarylene type difunctional epoxy resin(A), examples of the divinyl ether (a3′) of the other hydrocarboncompound include bisphenol A divinyl ether, bisphenolF divinyl ether,and hydroquinone divinyl ether.

The above step 1 is a step of reacting the difunctional phenol compound(a1′) with the divinyl ether (a2′) of the hydrocarbon compound having anether bond or the divinyl ether (a3′) of the other hydrocarbon compoundto produce a difunctional phenol resin as a raw material for epoxyresin.

Specifically, the desired difunctional phenol resin can be obtained bycharging the difunctional phenol compound (a1′) and the divinyl ether(a2′) of the hydrocarbon compound having an ether bond or the divinylether (a3′) of the other hydrocarbon compound in a reaction vessel andheating while mixing them with stirring.

In this case, an organic solvent can be optionally used. Examples of theorganic solvent include aromatic organic solvents such as benzene,toluene, and xylene; ketone organic solvents such as acetone,methylethyl ketone, methylisobutyl ketone, and cyclohexanone; andalcohol organic solvents such as methanol, ethanol, isopropyl alcohol,and normal butanol.

Although the reaction sufficiently proceeds without using a catalyst,the catalyst: can be appropriately used in view of selection of rawmaterials and an increase in reaction rate. Examples of usable catalystsinclude inorganic acids such as sulfuric acid, hydrochloric acid, nitricacid, and phosphoric acid; organic acids such as toluenesulfonic acid,methanesulfonic acid, xylenesulfonic acid, trifluoromethanesulfonicacid, oxalic acid, formic acid, trichloroacetic acid, andtrifluoroacetic acid; and Lewis acids such as aluminum chloride, ironchloride, tin chloride, gallium chloride, titanium chloride, aluminumbromide, gallium bromide, boron trifluoride-ether complex, and borontrifluoride-phenol complex. The amount of the catalyst is usually withina range from 10 ppm to 1% by weight based on the total weight of thedivinyl ether (a2′) of the hydrocarbon compound having an ether bond andthe divinyl ether (a3′) of the other hydrocarbon compound. In this case,the kind and the amount of the catalyst are preferably selected so asnot to cause the nucleus addition reaction of a vinyl group to thearomatic ring.

The reaction conditions in step 1 can be selected from a range from 25°C. to 200° C., and a temperature ranging from 50° C. to 150° C. ispreferable because proper reaction rate can be achieved. The reactiontime varies depending on the scale, but is preferably within a rangefrom 0.5 to 30 hours. In this case, the reaction is preferably carriedout in an oxygen atmosphere so as to prevent self-polymerization of avinyl ether group. The degree to which the reaction proceeds can bemonitored by measuring the residual amount of the raw material using gaschromatography or liquid chromatography. When using the organic solvent,the organic solvent is removed by distillation. When using the catalyst,the catalyst is optionally deactivated by a quencher and is removed by awashing or filtration operation. When using the organic solvent orcatalyst (including deactivated catalyst residue), which does notadversely affect the epoxidation reaction in the subsequent step, thepurification may be unnecessary.

A reaction ratio of the difunctional phenol compound (a1′) to thedivinyl ether (a2′) of the hydrocarbon compound having an ether bond orthe divinyl ether (a3′)of the; other hydrocarbon compound in the abovereaction may be appropriately selected according to properties of thedesired difunctional phenol resin. In the production of the flexibledifunctional epoxy resin (A), the amount of the divinyl ether (a2′) ofthe hydrocarbon compound having an ether bond or the divinyl ether (a3′)of the other hydrocarbon compound may be increased in order to enhancethe effect of improving flexibility, moisture resistance and dielectricproperties of the cured epoxy resin article.

Specifically, a ratio of a phenolic hydroxyl group in the difunctionalphenol compound (a1′) to a vinyl ether group in the divinyl ether (a2′)of the hydrocarbon compound having an ether bond or the divinyl ether(a3′) of the other hydrocarbon compound, (phenolic hydroxylgroup)/(vinyl ether group), is preferably from 80/20 to 50/50 (by molarratio). In the case in which a conversion ratio of the divinyl ether(a2′) of the hydrocarbon compound having an ether bond or the divinylether (a3′) of the other hydrocarbon compound is low due to an influenceof the side reaction, a proportion of the vinyl ether group may beincreased.

In the case of focusing on the balance between physical properties suchas curability and heat resistance, a ratio (phenolic hydroxylgroup)/(vinyl ether group) is preferably within a range from 95/5 to80/20 (by molar ratio).

In the production of the low dielectric difunctional epoxy resin (A),the amount of the divinyl ether compound (a3′) of the other hydrocarboncompound may be increased in order to enhance the effect of improvingflexibility, moisture resistance and dielectric properties of thedifunctional epoxy resin finally obtained.

Specifically, a ratio of a phenolic hydroxyl group in the difunctionalphenol compound (a1′) to a vinyl ether group in the divinyl ethercompound (a3′) of the other hydrocarbon compound, (phenolic hydroxylgroup)/(vinyl ether group) is preferably within a range from 80/20 to50/50 (by molar ratio).

In the case in which a conversion ratio of a divinyl ether group in thedivinyl ether compound (a3′) as the hydrocarbon compound is low due toan influence of the side reaction, the proportion of the vinyl ethergroup may be increased. In the case of focusing on the balance betweenphysical properties such as curability and heat resistance, the ratio(phenolic hydroxyl group)/(vinyl ether group) is preferably within arange from 95/5 to 80/20 (by molar ratio).

The structure of the difunctional phenol resin thus obtained variesdepending on the combination of raw materials. For example, when usingthe divinyl ether of the alkylene having 2 to 15 carbon atoms or thedivinyl ether represented by the general formula 10 as the raw materialof the flexible difunctional epoxy resin (A), examples of the resultingdifunctional phenol resin include those represented by the followingstructural formulas.

In the respective structures described above, n is a natural number, andthe average thereof is from 1.5 to 5. Bond-positions in the structurePa-16, are located independently on secondary carbon atoms which belongto ethylene or propylene consisting the aliphatic rings in thestructure. Examples of the compounds represented by the respectivestructural formulas include resins having a substituent such as methylgroup or halogen atom in the aromatic nucleus.

Among the difunctional phenol resins, a novel phenol resin representedby the following general formula 4:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or a bromine atom, X represents an ethyleneoxyethyl group, adi(ethyleneoxy)ethyl group, a tri(ethyleneoxy)ethyl group,propyleneoxypropyl group, a di(propyleneoxy)propyl group, atri(propyleneoxy)propyl group, or an alkylene group having 2 to 15carbon atoms, n is an natural number, and the average thereof is from1.5 to 5, is particularly preferable because the resulting cured epoxyresin article is excellent in balance between flexibility and toughnessand is also excellent in water resistance.

Specific examples of the novel phenol resin include the aforementionedcompounds of Pa-1 to Pa-14.

The difunctional phenol resin is obtained as a mixture of those havingstructural formulas of Pa-1 to Pa-17 wherein n=0. In the case of amixture of those having the structural formulas of Pa-1 to Pa-17, theaverage of n is preferably within a range from 1 to 4.5.

When using a divinyl ether having a cycloalkane structure as the rawmaterial of a low dielectric difunctional epoxy resin (A), typicalexamples thereof include those represented by the following structuralformulas.

In the respective structures described above, n is a natural number, andthe average thereof is from 1.5 to 5. Bond-positions in the structurePa-5 to 12, Pa-14 and Pa-15, are located independently on secondarycarbon atoms which belong to ethylene or propylene consisting thealiphatic rings in the structures.

The compounds represented by the respective structural formulas alsoinclude resins having a substituent such as methyl group or halogen atomin the aromatic nucleus.

Among the difunctional phenol resins, a novel phenol resin representedby the following general formula 5:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or a bromine atom, X represents a C₆₋₁₇ aliphatic hydrocarbon grouphaving a cycloalkane skeleton, n is a natural number, and the averagethereof is from 1.5 to 5, is particularly preferable because theresulting cured epoxy resin article is provided with proper flexibilitywhile maintaining excellent dielectric propertiesdielectric propertiesand is also excellent in toughness. Specific examples of the novelphenol resin include the aforementioned compounds of Pb-1 to Pb-8.

Since the resulting cured epoxy resin article is excellent in dielectricpropertiesdielectric properties, heat resistance, water resistance andfluidity, a novel phenol resin represented by the following generalformula 6:

wherein R₃ to R₆ each represents a hydrogen atom, a methyl group, achlorine atom, or a halogen atom, X each independently represents analiphatic cyclic hydrocarbon group having 6 to 15 carbon atoms, n is anatural number, and the average thereof is from 1.5 to 5, isparticularly preferable. Specific examples of the novel phenol resininclude the aforementioned compounds of Pb-9 to Pb-12.

The difunctional phenol resin is obtained as a mixture of those havingstructural formulas of Pb-1 to Pb-15 wherein n=0. In the case of amixture of those having the structural formulas of Pb-1 to Pb-15, theaverage of n is preferably within a range from 1.5 to 5.

The desired difunctional epoxy resin (A) can be produced by reacting thedifunctional phenol resin thus obtained with epihalohydrin in thesubsequent step 2. Examples of the epihalohydrin include epichlorohydrinand epibromohydrin.

Although the reaction conditions are not specifically limited in thereaction of step 2, the reaction is preferably carried out under theconditions of a temperature of 20° C. to 120° C. by or while adding analkali metal hydroxide such as sodium hydroxide or potassium hydroxidein a melted mixture of the difunctional phenol resin and epihalohydrin.The reaction time varies depending on the scale, but is preferably from1 to 10 hours. The amount of epihalohydrin is usually within a rangefrom 0.3 to 20 equivalents per equivalent of a hydroxyl group in thedifunctional phenol resin as the raw material. However, the greater theamount of excess epihalohydrin, the closer to the theoretical structurethe resulting difunctional epoxy resin becomes, and it becomes possibleto prevent formation of a secondary hydroxyl group due to the reactionbetween an unreacted phenolic hydroxyl group and an epoxy group. Theamount is preferably within a range from 2.5 to 20 equivalents from sucha point of view.

The alkali metal hydroxide may be used in the form of an aqueoussolution. In this case, the reaction can be conducted while continuouslyadding the aqueous solution of the alkali metal hydroxide in a reactionsystem and continuously distilling off water and epihalohydrin underreduced pressure or normal pressure. Furthermore, there can be applied amethod of removing water and continuously returning epihalohydrin intothe reaction system by partitioning the distillate.

There can also be used another method of adding a quaternary ammoniumsalt such as tetramethylammonium chloride, tetramethylammonium bromideor trimethylbenzylammonium chloride, as a catalyst, to a melted mixtureof the difunctional phenol resin and epihalohydrin, reacting the mixtureunder the conditions of a temperature of 50° C. to 150° C. to form ahalohydrin etherified product, adding an alkali metal hydroxide in thefrom of a solid or an aqueous solution, and reacting the mixture againunder the conditions of a temperature of 20° C. to 120° C., therebycausing dehydrohalogenation (cyclization). The reaction time is notspecifically limited, but is usually from 1 to 5 hours in the case of aproduction reaction of a halohydrin etherified product, and is from 1 to10 hours in the case of the dehydrohalogenation reaction.

In step 2, the reaction is preferably conducted by adding alcohols suchas methanol, ethanol, isopropyl alcohol, and butanol; ketones such asacetone and methyl ethyl ketone; ethers such as dioxane; and aproticpolar solvents such as dimethyl sulfone and dimethyl sulfoxide so thatthe reaction proceeds smoothly. The amount of the solvent is usuallyfrom 5 to 50% by weight, and is preferably from 10 to 30% by weight,based on the amount of epihalohydrin. When using the aprotic polarsolvent, the amount is usually from 5 to 100% by weight, and preferablyfrom 10 to 60% by weight, based on the amount of epihalohydrin.

The reaction product thus obtained is heated under reduced pressureunder conditions of a temperature of 110° C. to 250° C. and a pressureof 10 mmHg or less with or without washing with water, thereby removingepihalohydrin or other solvents added. In order to obtain an epoxy resincontaining a small amount of hydrolyzable halogen, it is preferable tosecurely cyclize a crude epoxy resin obtained after recoveringepihalohydrin by dissolving it again in a solvent such as toluene ormethyl isobutyl ketone, adding an aqueous solution of an alkali metalhydroxide such as sodium hydroxide or potassium hydroxide and reactingthe mixture.

In this case, the amount of the alkali metal hydroxide is usually from0.5 to 10 mol, and preferably from 1.2 to 5.0 mol, per mol ofhydrolyzable chlorine remaining in the crude epoxy resin. The reactiontemperature is usually from 50° C. to 120° C., while the reaction timeis usually from 0.5 to 3 hours. For the purpose of improving thereaction rate, phase transfer catalysts such as quaternary ammonium saltand crown ether may be added. When using the phase transfer catalyst,the amount is preferably within a range from 0.1 to 3.0% by weight basedon the crude epoxy resin.

After the completion of the reaction, the produced salt is removed byfiltration or washing with water and the solvent such as toluene ormethyl isobutyl ketone is removed by heating under reduced pressure toobtain the desired difunctional epoxy resin (A).

A preferable method used in the steps 1 and 2 is a method of producing adifunctional phenol resin in step 1, charging raw materials such asepihalohydrins without taking out the resulting difunctional phenolresin from a reaction vessel and reacting the mixture in step 2 in viewof good productivity.

As described above, the difunctional epoxy resin (A) produced by passingthrough the steps 1 and 2 is produced as a mixture with the difunctionalepoxy resin (A′) having a structure wherein a glycidyloxy group isbonded to the aromatic nucleus of the aromatic hydrocarbon group (a1)having a bonding site with the other group in the aromatic nucleus. Inthe epoxy resin composition of the present invention, the mixture can beused as it is as an epoxy resin component.

As long as the effects of the present invention are not adverselyaffected, in the epoxy resin composition of the present invention, theepoxy resin mixture can be used in combination with other epoxy resins.When using the flexible difunctional epoxy resin (A) in underfillmaterials in the field of semiconductor encapsulantsemiconductorencapsulant or in common coatings, liquid epoxy resins such as bisphenolA type epoxy resin, bisphenol F type epoxy resin, anddihydroxynaphthalene type epoxy resin can be used in combination. In thecase of applications such as flexible wiring boards, brominated epoxyresins such as brominated phenol novolak type epoxy resin can be used incombination with solid bisphenol A type epoxy resins. The content ofthese other epoxy resin, which can be used in combination, is preferablyless than 60% by weight based on the epoxy resin composition of thepresent invention. Two or more kinds of these epoxy resins may be usedin combination.

It is possible to partially use flexible difunctional epoxy resins (A)in combination for the purpose of imparting flexibility to rigid epoxyresins such as phenol novolak type epoxy resin, cresol novolak typeepoxy resin, triphenylmethane type epoxy resin, tetraphenylethane typeepoxy resin, dicyclopentadiene-phenol addition reaction type epoxyresin, phenolaralkyl type epoxy resin, naphthol novolak type epoxyresin, naphtholaralkyl type epoxy resin, naphthol-phenol co-condensationnovolak type epoxy resin, naphthol-cresol co-condensation novolak typeepoxy resin, aromatic hydrocarbon formaldehyde resin-modified phenolresin type epoxy resin, and biphenyl-modified novolak type epoxy resin.

When using the low dielectric difunctional epoxy resin (A), inapplications such as semiconductor encapsulantsemiconductor encapsulant,examples thereof include liquid epoxy resins such as bisphenol A typeepoxy resin, bisphenol F type epoxy resin, and dihydroxynaphthalene typeepoxy resin; and biphenyl type epoxy resin, tetramethylbiphenyl typeepoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxyresin, triphenylmethane type epoxy resin, tetraphenylethane type epoxyresin, dicyclopentadiene-phenol addition reaction type epoxy resin,phenolaralkyl type epoxy resin, naphthol novolak type epoxy resin,naphtholaralkyl type epoxy resin, naphthol-phenol co-condensationnovolak type epoxy resin, naphthol-cresol co-condensation novolak typeepoxy resin, aromatic hydrocarbon formaldehyde resin-modified phenolresin type epoxy resin, and biphenyl-modified novolak type epoxy resin.

When using the low dielectric difunctional epoxy resin (A), inapplications such as electrical laminates, brominated epoxy resins suchas brominated phenol novolak type epoxy resin can be used in combinationwith solid bisphenol A type epoxy resins, in addition to the liquidepoxy resins. The content of the epoxy resin, which can be used incombination, is preferably less than 70% by weight, and particularlypreferably less than 60% by weight, based on the epoxy resin compositionof the present invention. Two or more kinds of these epoxy resins may beused in combination.

It should be noted that when the difunctional epoxy resin (A) ismanufactured and when the above alicyclic structure-containing phenolsor xylok-type phenol resins are used as the difunctional phenol compound(a1′), there may be not only difunctional components but alsotrifunctional components at the same time. As described above, suchalicyclic structure-containing phenols or xylok-type phenol resins whichhave multifunctional components can be reacted as they are with adivinyl ether (a2′) of a hydrocarbon compound having an ether bond or adivinyl ether (a3′) of the other hydrocarbon compound according to thepresent invention. Accordingly, in this case, the difunctional epoxyresin (A) which is finally obtained is in a mixture epoxy resins whichinclude a trifunctional or higher components, and such a mixture as itis can be used for various purposes.

As the curing agent (B) in the epoxy resin composition of the presentinvention, various curing agents for epoxy resin can be used andexamples thereof include amine compounds, acid anhydride compounds,amide compounds and phenol compounds.

Examples of the amine compounds include aliphatic polyamines such asethylenediamine, propylenediamine, butylenediamine,hexamethylenediamine, diethylenetriamine, triethylenetetramine,pentaethylenehexamine, and triethylenetetramine; amines having a highmolecular weight such as polypropyleneglycoldiamines having a molecularweight of 200 to 500; aromatic polyamines such as metaxylylenediamine,diaminodiphenylmethane, and phenylenediamine; alicyclic polyamines suchas 1,3-bis(aminomethyl)cyclohexane, isophoronediamine, andnorbornanediamine; and polyamide resins synthesized from a dimer ofdicyandiamine or linolenic acid and ethylenediamine.

Examples of the acid anhydride compounds include phthalic anhydride,trimellitic anhydride, pyromellitic anhydride, maleic anhydride,tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylnadic anhydride, hexahydrophthalic anhydride, andmethylhexahydrophthalic anhydride.

Examples of the phenol compounds include phenol novolak resin, cresolnovolak resin, aromatic hydrocarbon formaldehyde resin-modified phenolresin, dicyclopentadienephenol addition type resin, phenolaralkyl resin,naphtholaralkyl resin, trimethylolmethane resin, tetraphenylolethaneresin, naphthol novolak resin, naphthol-. phenol co-condensation novolakresin, naphthol-cresol co-condensation novolak resin, biphenyl-modifiedphenol resin, and aminotriazine-modified phenol resin, or modifiedcompounds thereof. Examples of the latent catalyst include imidazole,BF₃-amine complex, and guanidine derivative.

These curing agents such as amine compounds, acid anhydride compounds,amide compounds and phenol compounds may be used alone, or two or morekinds thereof may be used in combination.

In applications such as use in underfill materials and use in commoncoatings, the acid anhydride compounds or amine compounds are preferablyused. In applications such as adhesives, the amine compounds arepreferable. In applications such as flexible wiring boards, the aminecompounds, particularly dicyandiamine is preferable in view ofoperability and curability. In the field in which flexibility of curedarticles is demanded, it is preferred that the above amine having a highmolecular weight be used as a curing agent. In applications such assemiconductor encapsulant, solid type phenol compounds are preferable inview of heat resistance of the article.

In the epoxy resin composition of the present invention, the amount ofthe curing agent (B) is preferably controlled so that an equivalent ofan active hydrogen group in the curing agent (B) is from 0.7 to 1.5equivalents per 1 equivalent of epoxy group in the entire epoxycomponents in the composition because curing proceeds smoothly and goodphysical properties of a cured article are obtained.

In the epoxy resin composition of the present invention, curingaccelerating agents can be appropriately used. Examples of the curingaccelerating agent include phosphorus compound, tertiary amine,imidazole, organic acid metal salt, Lewis acid, and amine complex salt.These curing accelerating agents can be used alone, or two or more kindsthereof can be used in combination. In applications such assemiconductor encapsulant, phosphorus compounds such astriphenylphosphine and amine compounds such as DBU are preferablebecause of excellent curability, heat resistance, electricalcharacteristics and moisture-resistant reliability.

The epoxy resin composition of the present invention may containinorganic fillers according to applications. Examples of the inorganicfiller include fumed silica, crystalline silica, alumina, siliconnitride, and aluminum hydroxide. When the amount of the inorganic filleris particularly large, fumed silica is preferably used. Although eitherof crushed fumed silica and spherical fumed silica can be used,spherical fumed silica is preferably used so as to increase the amountof the fumed silica and to suppress an increase in melt viscosity of amolding material. To increase the amount of the spherical silica, sizedistribution of the spherical silica is preferably adjusted. The higherthe filling factor, the better, in view of the flame resistance. Thefilling factor is particularly preferably at least 65% by weight basedon the total amount of the epoxy resin composition. In applications suchas conductive pastes, conductive fillers such as silver powder andcopper powder can be used.

If necessary, various additives such as silane coupling agents,relesants, pigments, and emulsifiers can be used in the epoxy resincomposition of the present invention, and also fire retardants can beused. Examples of the fire retardant include halogen compounds such asdecabromodiphenyl ether and tetrabromobisphenol A; phosphorus-containingcompounds such as red phosphorus and various phosphate ester compounds;nitrogen-containing compounds such as melamine and its derivatives; andinorganic flame-retardant compounds such as aluminum hydroxide,magnesium hydroxide, zinc borate, and calcium borate.

The epoxy resin composition of the present invention is obtained byuniformly mixing the respective components described above. For example,an epoxy resin composition for coating is prepared by uniformly mixingan epoxy resin, a curing agent and, if necessary, additives such asorganic solvents, fillers and pigments using a disperser such as paintshaker.

As described above, a cured article of a composition containing theflexible difunctional epoxy resin (A) is flexible and has toughness and,therefore, it is suited for applications such as underfill materials inthe field of semiconductor encapsulantsemiconductor encapsulant andflexible wiring boards in the field of electrical laminates, which haverecently been much in demand. Also, a composition containing the lowdielectric difunctional epoxy resin (A) yields a cured epoxy resinarticle which has low dielectric constant and low dielectric dissipationfactor and is also excellent in moisture resistance and waterresistance. Therefore, these compositions are suited for applicationssuch as semiconductor encapsulantsemiconductor encapsulant, andelectrical laminates such as printed circuit boards.

A melt-mixing type epoxy resin composition suited for applications suchas underfill materials and semiconductor encapsulant is prepared byuniformly mixing a mixture of the difunctional epoxy resin (A) and thedifunctional epoxy resin (A′), a curing agent (B), fillers and, ifnecessary, other epoxy resins using an extruder, a kneader or a roll. Inthat case, silica is commonly used as the filler. The amount of thefiller is preferably within a range from 30 to 95% by weight based on100 parts by weight of the epoxy resin composition, and particularlypreferably at least 70% by weight, in order to improve flame resistance,moisture resistance, and solder cracking resistance, and to decrease thelinear expansion coefficient. An underfill material made of thecomposition is produced by molding the composition using a casting ortransfer molding machine, or an injection molding machine and curingwith heating at 80° C. to 200° C. for 2 to 10 hours.

An epoxy resin composition for flexible wiring board materials, otherelectrical laminates, and CFRP is prepared by dissolving the epoxy resincomposition in a solvent such as toluene, xylene, acetone, methyl ethylketone, or methyl isobutyl ketone to form a varnish-like composition. Inthis case, the amount of the solvent is usually from 10 to 70 parts byweight, preferably from 15 to 65 parts by weight, based on 100 parts byweight of the mixture of the epoxy resin composition of the presentinvention and the solvent. A laminate made of the epoxy resincomposition is produced by impregnating a base material such as glassfibers, carbon fibers, polyester fibers, polyamide fibers, aluminafibers, and paper with an epoxy resin composition solution (varnish-likecomposition) and drying the impregnated base material by heating to forma prepreg, followed by hot press forming.

The epoxy resin composition of the present invention can form curedarticles such as molded article, laminate, cast, adhesive, coating film,and film in various applications by a thermocuring process.

EXAMPLES

The present invention will be described in detail by way of examples andcomparative examples. In the following Examples and ComparativeExamples, parts and percentages are by weight unless otherwisespecified.

Example 1 (Synthesis of Difunctional Phenol Resin of Structural FormulaPa-1)

To a flask equipped with a thermometer and a stirrer, 228 g (1.00 mol)of bisphenol A and 172 g (0.85 mol) of triethylene glycol divinyl ether(manufactured by ISP Co. under the trade name “Rapi-Cure DVE-3”) werecharged, heated to 120° C. over one hour and then reacted at 120° C. for6 hours to obtain 400 g of transparent semisolid modified polyhydricphenols (ph-1a).

It was confirmed, from an NMR spectrum (¹³C) shown in FIG. 1 and fromthe fact that peaks of M+=658 and M+=1088 corresponding to theoreticalstructures of n=1 and n=2 were obtained in a mass spectrum, that theresulting modified polyhydric phenols (ph-1a) have a structurerepresented by the above general formula Pa-1. A hydroxyl groupequivalent was 364 g/eq, viscosity was 40 mPa·s (150° C., ICIviscometer), and an average value of n in the structural formula P-1calculated from the hydroxyl group equivalent was 3.21 in the case ofthe component of n≧1 and was 11.6 in the case of the component of n≧0.

Example 2 (Synthesis of Difunctional Epoxy Resin of Structural FormulaEa-1)

To a flask equipped with a thermometer, a dropping funnel, a coolingtube and a stirrer, 400 g (hydroxyl group equivalent: 364 g/eq) of themodified polyhydric phenols (ph-1a) obtained in Example 1, 925 g (10mol) of epichlorohydrin and 185 g of n-butanol were charged anddissolved. After heating to 65° C. while purging with nitrogen gas, thepressure was reduced to an azeotropic pressure, and 122 g (1.5 mol) ofan aqueous 49% sodium hydroxide solution was added dropwise over 5hours. Under these conditions, the mixture was continuously stirred for0.5 hours. The distillate produced during the azeotropic reaction wasisolated by a Dean-Stark trap and the aqueous layer was removed, andthen the reaction was conducted while returning the organic layer in thereaction. The unreacted epichlorohydrin was distilled off under reducedpressure. The resulting crude epoxy resin was dissolved by adding 1000 gof methyl isobutyl ketone and 100 g of n-butanol. To the solution, 20 gof an aqueous 10% sodium hydroxide solution was added and the reactionwas conducted at 80° C. for 2 hours. Then, the reaction solution waswashed with 300 g of water three times until the wash was neutral. Waterwas removed from the reaction system by azeotropy, then precisionfiltration was carried out, and then the solvent was distilled off underreduced pressure to obtain 457 g of an epoxy resin (ep-1a) of atransparent liquid. It was confirmed, from an NMR spectrum (¹³C) shownin FIG. 2 and from the fact that peaks of M⁺=770 and M⁺=1200corresponding to theoretical structures of n=1 and n=2 were obtained ina mass spectrum, that the epoxy resin (ep-1a) contains an epoxy resinhaving a structure represented by the general formula Ea-1.

The resulting epoxy resin (ep-1a) is a mixture of a compound of thestructural formula Ea-1 wherein n=0 and a compound wherein n=1 or more.The results of GPC revealed that the mixture contains 20% by weight ofthe compound wherein n=0. An epoxy equivalent of this epoxy resin(ep-1a) was 462 g/eq, viscosity was 12000 mPa·s (25° C., Cannon-Fenskemethod), and an average value of n in the structural formula Ea-1calculated from the epoxy equivalent was 2.97 in the case of thecomponent of n≧1 and was 1.35 in the case of the component of n≧0.

Example 3 (Synthesis of Difunctional Phenol Resin of Structural FormulaPa-1)

In the same manner as in Example 1, except that the amount of thetriethylene glycol divinyl ether (DVE-3) was replaced by 101 g, modifiedpolyhydric phenols (ph-2a) were obtained. A hydroxyl group equivalent ofthe resulting modified polyhydric phenols (ph-2a) was 262 g/eq,viscosity was 60 mPa·s (150° C., ICI viscosmeter), and an average valueof n in the structural formula Pa-1 calculated from the hydroxyl groupequivalent was 2.21 in the case of the component of n≧1 and was 0.69 inthe case of the component of n≧0.

Example 4 (Synthesis of Difunctional Epoxy Resin of Structural FormulaEa-1)

In the same manner as in Example 2, except that modified polyhydricphenols (ph-1a) as the raw material were replaced by 329 g of modifiedpolyhydric phenols (ph-2a), 395 g of an epoxy resin (ep-2a) wasobtained. The resulting epoxy resin (ep-2a) was a mixture of a compoundof the structural formula Ea-1 wherein n=0 and a compound wherein n=1 ormore. The results of GPC revealed that the mixture contains 30% byweight of the compound wherein n=0. An epoxy equivalent of this epoxyresin (ep-2a) was 350 g/eq, viscosity was 90000 mPa·s (25° C., E typeviscometer), and an average value of n in the structural formula E-1calculated from the epoxy equivalent was 2.18 in the case of thecomponent of n≧1 and was 0.84 in the case of the component of n≧0.

Example 5 (Synthesis of Difunctional Phenol Resin of Structural FormulaPa-1)

In the same manner as in Example 1, except that the amount of thetriethylene glycol divinyl ether (DVE-3) was replaced by 192 g, modifiedpolyhydric phenols (ph-3a) were obtained. A hydroxyl group equivalent ofthe resulting modified polyhydric phenols was 423 g/eq, viscosity was 30mPa·s (150° C., E ICI viscometer), and an average value of n in thestructural formula P-1 calculated from the hydroxyl group equivalent was3.23 in the case of the component of n≧1 and was 1.43 in the case of thecomponent of n≧0.

Example 6 (Synthesis of Difunctional Epoxy Resin of Structural FormulaEa-1)

In the same manner as in Example 2, except that modified polyhydricphenols (ph-1a) as the raw material were replaced by 420 g of modifiedpolyhydric phenols (ph-3a), 471 g of an epoxy resin (ep-3a) wasobtained. The resulting epoxy resin (ep-3a) was a mixture of a compoundof the structural formula E-1 wherein n=0 and a compound wherein n=1 ormore. The results of GPC revealed that the mixture contains 15% byweight of the compound wherein n=0. An epoxy equivalent of this epoxyresin (ep-3a) was 526 g/eq, viscosity was 4700 mPa·s (25° C.,Cannon-Fenske method), and an average value of n in the structuralformula E-1 calculated from the epoxy equivalent was 3.08 in the case ofthe component of n≧1 and was 1.65 in the case of the component of n≧0.

Synthesis Example 1 (Synthesis of Dimer Acid-Modified Epoxy Resin)

To a flask equipped with a thermometer, a cooling tube and a stirrer,457 g of a bisphenol A type liquid epoxy resin (manufactured byDainippon Ink and Chemicals, Inc., under the trade name “EPICLON 850S”,epoxy equivalent: 185 g/eq) and 243 g of dimer acid (manufactured byTsuno Food Industrial Co., Ltd., under the trade name “Tsunodyme 216”)were charged and heated to 80° C. while purging with nitrogen gas. Then,0.14 g of triphenylphosphine (catalyst) was added, and the mixture wasreacted at 140° C. for 2 hours to obtain 700 g of a semisolid epoxyresin (ep-4a). The resulting epoxy resin (ep-4a) had a structure whereina molecular chain is extended by an ester bond as a result of thereaction between carboxyl groups of the dimer acid and epoxy groups, andhad an epoxy equivalent of 451 g/eq and a viscosity of 170 mPa·s (150°C., ICI viscometer).

Synthesis Example 2 (Synthesis of Sebacic Acid-Modified Epoxy Resin)

In the same manner as in Synthesis Example 1, except that the dimer acidwas replaced by 119 g of sebacic acid (reagent), 576 g of a semisolidepoxy resin (ep-5b) was obtained. The resulting epoxy resin had astructure wherein a molecular chain was extended by an ester bond as aresult of the reaction between carboxyl groups of the dimer acid andepoxy groups, and had an epoxy equivalent of 488 g/eq and a viscosity of290 mPa·s (150° C., ICI viscometer).

Examples 7 to 11 and Comparative Examples 1 to 3

Using three kinds of the epoxy resins (ep-1a) to (ep-3a) synthesizedabove, and the dimer acid-modified epoxy resin (ep-4a) and the sebacicacid-modified epoxy resin (ep-5a) for comparison obtained in SynthesisExamples 1 and 2 and a 6EO-modified bisphenol A type epoxy resin (ep-6a,manufactured by New Japan Chemical Co., Ltd., under the trade name “RikaResin BEO-60E”, epoxy equivalent: 358 g/eq) as a glycidyl ether of anethylene oxide adduct (6 mol addition) of bisphenol A, performances wereevaluated. As the epoxy resin used in combination with the epoxy resins(ep-1a) and (ep-2a), a bisphenol A type liquid epoxy resin (ep-7a,manufactured by Dainippon Ink and Chemicals, Inc., under the trade name“EPICLON 850S”, epoxy equivalent: 188 g/eq) was used.

(Bending resistance) According to the formulation shown in Table 1, anepoxy resin, an amine curing agent (triethylenetetramine) and xylenewere uniformly mixed at room temperature. The mixture was charged in aniron dish (65 mm in diameter, 12 mm in height) and heated at 80° C. for2 hours, then at 125° C. for 2 hours to obtain a 2 mm thick curedarticle. Using the resulting cured article, a bending test was conductedand the bending resistance was evaluated. The bending test was conductedby bending the cured article by about 180° and it was confirmed whetheror not cracking and peeling of the bent portion occur. Samples wherecracking of the bent portion was observed were rated “poor”, whileSamples where cracking of the bent portion was observed were rated“good”.

(Adhesion) According to the formulation shown in Table 1, an epoxyresin, an amine curing agent (triethylenetetramine) and xylene wereuniformly mixed at room temperature. The mixture was applied on a coldrolled steel sheet(0.8 mm×70 mm×150 mm, SPCC-SB, treated with awater-resistant sand paper (#240)) and heated at 80° C. for 48 hours toobtain a 50 μm thick test piece. Using the resulting test piece, a crosscut test was conducted and the adhesion was evaluated. The cross cuttest was conducted according to JIS K5400-6.15 and the results wereevaluated by the number of remaining coating sections.

(Moisture resistance) According to the formulation shown in Table 1, anepoxy resin, an amine curing agent (triethylenetetramine) and xylenewere uniformly mixed at room temperature. The mixture was charged in aniron dish (65 mm in diameter, 12 mm in height) and heated at 80° C. for2 hours, then at 125° C. for 2 hours to obtain a 2 mm thick curedarticle. Using the resulting cured article, a pressure cooker test wasconducted and the moisture resistance was evaluated. The pressure cookertest was conducted under the conditions of 121° C., 100% RH and 2 atmfor 5 hours. Defects such as cracking, breakage, discoloration, andfogging of the cured article were visually observed. Samples withdefects were rated “poor”, while samples with no defects were rated“good”. Also, a water absorption ratio was calculated from an increasein weight after the pressure cooker test.

(Bondability) According to the formulation shown in Table 1, an epoxyresin, an amine curing agent (triethylenetetramine) and xylene wereuniformly mixed at room temperature. The mixture was applied on a coldrolled steel sheet (1.6 mm×25 mm×100 mm, SPCC-SB manufactured byTest-Piece Co., degreased with toluene) and heated at 80° C. for 2hours, then at 125° C. for 2 hours and 150° C. for 2 hours to obtain atest piece. Using the resulting test piece, a tensile shear test wasconducted and the bondability was evaluated. The tensile shear test wasconducted according to JIS K6850 and a rupture stress (MPa) wascompared. Also an aluminum sheet (1.6 mm×25 mm×100 mm, A1050Pmanufactured by Test-Piece Co., degreased with toluene) was evaluated inthe same manner.

TABLE 1 Examples Comparative Examples 7 8 9 10 11 1 2 3 FormulationEpoxy resin (ep-1a) 66.5 45.5 Epoxy resin (ep-2a) 65.5 45.1 Epoxy resin(ep-3a) 66.9 Epoxy resin (ep-4a) 66.5 Epoxy resin (ep-5a) 66.7 Epoxyresin (ep-6a) 65.6 Epoxy resin (ep-7a) 19.5 19.3 Triethylenetetramine3.5 4.5 3.1 5.0 5.6 3.5 3.3 4.4 Xylene 30.0 30.0 30.0 30.0 30.0 30.030.0 30.0 Bending test Good Good Good Good Good Poor Poor Poor Adhesion(cross cut test) 100/100 100/100 100/100 100/100 100/100 90/100 87/100100/100 Moisture resistance Good Good Good Good Good Poor Poor PoorMoisture adsorption rate 1.85 1.77 1.90 1.72 1.68 2.10 2.08 7.20Bondability Cold rolled steel sheet (Mpa) 17.0 15.2 17.5 12.2 10.2 6.05.9 10.1 Aluminum sheet (Mpa) 11.0 9.0 11.5 8.9 7.5 5.0 4.8 7.3

Example 12 (Synthesis of Difunctional Phenol Resin of Structural FormulaPb-1)

To a flask equipped with a thermometer and a stirrer, 228 g (1.00 mol)of bisphenol A and 144 g of 1,4-cyclohexanedimethanol divinyl ether(manufactured by Nippon Carbide Industries Co., Inc., under the tradename “CHDVE”) were charged, heated to 120° C. over one hour and thenreacted at 120° C. for 6 hours to obtain 372 g of a transparent solidphenol resin (ph-1b). It was confirmed, from an NMR spectrum (¹³C) shownin FIG. 3 and from the fact that peaks of M⁺=652 and M⁺=1076corresponding to theoretical structures of n=1 and n=2 were obtained ina mass spectrum, that the resulting resin is the desired difunctionalphenol resin having a structure represented by the general formula P-1.A hydroxyl group equivalent was 389 g/eq, viscosity at 150° C. was 140mPa·s (ICI viscometer), and an average value of n in the structuralformula Pb-1 calculated from the hydroxyl group equivalent was 2.66 inthe case of the component of n≧1 and 1.30 in the case of the componentof n≧0.

Example 13 (Synthesis of Difunctional Epoxy Resin of Structural FormulaEb-1)

To a flask equipped with a thermometer, a dropping funnel, a coolingtube and a stirrer, 372 g of the modified polyhydric phenols (ph-1b)obtained in Example 1, 925 g (10 mol) of epichlorohydrin and 185 g ofn-butanol were charged and dissolved. After heating to 65° C. whilepurging with nitrogen gas, the pressure was reduced to an azeotropicpressure, and 122 g (1.5 mol) of an aqueous 49% sodium hydroxidesolution was added dropwise over 5 hours. Under these conditions, themixture was continuously stirred for 0.5 hours. The distillate producedduring the azeotropic reaction was isolated by a Dean-Stark trap and theaqueous layer was removed, and then the reaction was conducted whilereturning the organic layer in the reaction. The unreactedepichlorohydrin was distilled off under reduced pressure. The resultingcrude epoxy resin was dissolved by adding 1000 g of methyl isobutylketone and 100 g of n-butanol. To the solution, 20 g of an aqueous 10%sodium hydroxide solution was added and the reaction was conducted at80° C. for 2 hours. Then, the reaction solution was washed with 300 g ofwater three times until the wash was neutral. The system was dehydratedby azeotropy and subjected to precise filtration, and then the solventwas distilled off under reduced pressure to obtain 422 g of an epoxyresin (ep-1b) of a transparent liquid.

It was confirmed, from an NMR spectrum (¹³C) shown in FIG. 2 and fromthe fact that peaks of M⁺=764 and M⁺=1188 corresponding to theoreticalstructures of n=1 and n=2 were obtained in a mass spectrum, that theepoxy resin (ep-1b) contains an epoxy resin having a structurerepresented by the general formula Eb-1.

The resulting epoxy resin (ep-1b) is a mixture of a compound of thestructural formula E-1 wherein n=0 and a compound wherein n=1 or more.The results of GPC revealed that the mixture contains 15% by weight ofthe compound wherein n=0. An epoxy equivalent of this epoxy resin(ep-1b) was 490 g/eq, viscosity at 150° C. was 130 mPa·s (ICIviscometer), and an average value of n in the structural formula Eb-1calculated from the epoxy equivalent was 2.66 in the case of thecomponent of n≧1 and 1.51 in the case of the component of n≧0.

Example 14 (Synthesis of Difunctional Phenol Resin of Structural FormulaPb-9)

In the same manner as in Example 1, except that bisphenol A as the rawmaterial was replaced by 294 g of a dicyclopentadiene-modified phenolresin (manufactured by Nippon Petrochemicals Co., Ltd., under the tradename “Nisseki Special Phenol Resin DPP-6085”) and DVE-3 was replaced by64 g of CHDVE, 358 g of a brown solid difunctional phenol resin (ph-2b)was obtained. It was confirmed, from an NMR spectrum (¹³C) shown in FIG.5 and from the fact that peaks of M⁺=836 and M⁺=1352 corresponding totheoretical structures of n=1 and n=2 were obtained in a mass spectrum,that the resulting resin is the desired difunctional phenol resin havinga structure represented by the general formula Pb-9. A hydroxyl groupequivalent was 265 g/eq, viscosity at 150° C. was 710 mPa·s (ICIviscometer), and an average value of n in the structural formula Pb-9calculated from the hydroxyl group equivalent was 1.37 in the case ofthe component of n≧1 and 0.41 in the case of the component of n≧0.

Example 15 (Synthesis of Difunctional Epoxy Resin of Structural FormulaEb-9)

In the same manner as in Example 2, except that modified polyhydricphenols (ph-1b) as the raw material were replaced by 358 g of modifiedpolyhydric phenols (ph-2b), 429 g of a brown solid difunctional epoxyresin (ep-2b) was obtained. It was confirmed, from an NMR spectrum (¹³C)shown in FIG. 6 and from the fact that peaks of M⁺=948 and M⁺=1464corresponding to theoretical structures of n=1 and n=2 were obtained ina mass spectrum, that the resulting resin is the desired difunctionalphenol resin having a structure represented by the general formula Eb-9.The resulting epoxy resin was a mixture of a compound of the structuralformula Eb-9 wherein n=0 and a compound wherein n=1 or more. The resultsof GPC revealed that the mixture contains 35% by weight of the compoundwherein n=0. An epoxy equivalent was 353 g/eq, viscosity at 150° C. was190 mPa·s (ICI viscometer), and an average value of n in the structuralformula Eb-9 calculated from the hydroxyl group equivalent was 1.44 inthe case of the component of n≧1 and 0.53 in the case of the componentof n≧0.

Examples 16 and 17, and Comparative Examples 4 to 7

According to the formulation shown in Table 2, an epoxy resin, a phenolnovolak resin curing agent (manufactured by Dainippon Ink and Chemicals,Inc., under the trade name “Phenolite TD-2131”, hydroxyl groupequivalent: 104 g/eq) and triphenylphosphine (accelerator) wereuniformly mixed at 120° C. and then press-formed at a temperature of150° C. for 10 minutes. Then, the preform was post-cured at 175° C. for5 hours to obtain a cured article. A test piece having a predeterminedsize was cut from the cured article and then heat resistance, moistureresistance and dielectric propertiesdielectric properties were evaluatedby using the resulting test piece. The heat resistance was evaluated bymeasuring the glass transition temperature using a dynamicviscoelasticity testing machine, while the moisture resistance wasevaluated by using an increase in weight after treating by the pressurecooker test (121° C., 100% RH, 2 atm×2 times) as a moisture adsorptionratio. The dielectric propertiesdielectric properties were measuredunder the conditions of 1 MHz/25° C. using a dielectric constantmeasuring device (manufactured by Japan E.M. Co., Ltd., “DPMS1000”).

The epoxy resins used for comparison include a bisphenol A type liquidepoxy resin (ep-3b, manufactured by Dainippon Ink and Chemicals, Inc.,under the trade name “EPICLON 850S”, epoxy equivalent: 188 g/eq), abisphenol A type solid epoxy resin (ep-4b, manufactured by Dainippon Inkand Chemicals, Inc., under the trade name “EPICLON 1055”, epoxyequivalent: 477 g/eq), a cresol novolak type epoxy resin (ep-5b,manufactured by Dainippon Ink and Chemicals, Inc., under the trade name“EPICLON N-665-EXP”, epoxy equivalent: 203 g/eq), and adicyclopentadiene type epoxy resin (ep-6b, manufactured by Dainippon Inkand Chemicals, Inc., under the trade name “EPICLON HP-7200H”, epoxyequivalent: 279 g/eq).

TABLE 2 Examples Comparative_Examples 16 17 4 5 6 7 Formulation Epoxyresin (ep-1b) 82 Epoxy resin (ep-2b) 77 Epoxy resin (ep-3b) 64 Epoxyresin (ep-4b) 82 Epoxy resin (ep-5b) 66 Epoxy resin (ep-6b) 73 TD-213118 23 36 18 34 27 Triphenylphosphine 1 1 1 1 1 1 Evaluation Glasstransition temperature 84 133 134 115 180 174 (° C.) Moisture adsorptionratio (%) 1.03 0.57 1.6 1.89 1.05 0.59 Dielectric constant 3.69 3.564.76 4.4 4.43 3.93 Dielectric dissipation factor 0.021 0.013 0.041 0.0430.026 0.019

While preferred embodiments of the-invention have been described andillustrated above, it should be understood that these are exemplary ofthe invention and are not to be considered as limiting. Additions,omissions, substitutions, and other modifications can be made withoutdeparting from the spirit or scope of the present invention.Accordingly, the invention is not to be considered as being limited bythe foregoing description, and is only limited by the scope of theappended claims.

1. An epoxy resin represented by the following general formula 1:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or a bromine atom, X represents an ethyleneoxyethyl group, adi(ethyleneoxy)ethyl group, a tri(ethyleneoxy)ethyl group, apropyleneoxypropyl group, a di(propyleneoxy)propyl group, atri(propyleneoxy)propyl group, or an alkylene group having 2 to 15carbon atoms, n is a natural number, and the average thereof is from 1.2to
 5. 2. An epoxy resin represented by the following general formula 2:

wherein R₁ and R₂ each represents a hydrogen atom or a methyl group, R₃to R₆ each represents a hydrogen atom, a methyl group, a chlorine atom,or a bromine atom, X represents a C₆₋₁₇ aliphatic hydrocarbon grouphaving a cycloalkane skeleton, n is a natural number, and the averagethereof is from 1.2 to
 5. 3. An epoxy resin represented by the followinggeneral formula 3:

wherein R₃ to R₆ each represents a hydrogen atom, a methyl group, achlorine atom, or a bromine atom, X each independently represents aC₆₋₁₇ aliphatic hydrocarbon group having a cycloalkane skeleton, n is anatural number, and the average thereof is from 1.2 to 5.